• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.131-136
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• 2006

Commercial uses of GPS have been growing rapidly with applications for aircraft, ship, and land vehicle navigation as well as for surveying and time keeping. The next generation GPS and Japanese QZS (Quasi Zenith Satellite) will provide three different civil signals. Galileo will also provide several types of civil signals. The availability of the third civil frequency has obvious advantages to instantaneous carrier phase accuracy and ambiguity resolution for centimeter level measurements. This paper discusses the effects of additional new civil signals for the high accuracy positioning in urban areas based on simulation using practical raw data. As for constellation, only GPS and GPS+QZS are considered. For positioning, a short distance baseline is assumed in order to disregard atmosphere effects. In this simulation, mask angle and signal conditions were fixed and ambiguity success rates were compared between different triple frequency combination scenarios. The coefficient of reflection was set randomly from 0.05 to 0.5 and the multipath delay was also set randomly from 5-100 m. Visible satellites and signal strength were determined by raw data collected in Tokyo by car. These simulation results have confirmed that the availability of high accuracy positioning will increase in all scenarios if we use GPS+QZS with triple frequencies.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.02a
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• pp.82-94
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• 2004

This paper addresses solutions to the challenges of carrier phase integer ambiguity resolution and cycle slip detection/identification, for maintaining high accuracy of an integrated GPS/Pseudolite/INS system. Such a hybrid positioning and navigation system is an augmentation of standard GPS/INS systems in localized areas. To achieve the goal of high accuracy, the carrier phase measurements with correctly estimated integer ambiguities must be utilized to update the system integration filter's states. The occurrence of a cycle slip that is undetected is, however, can significantly degrade the filter's performance. This contribution presents an effective approach to increase the reliability and speed of integer ambiguity resolution through using pseudolite and INS measurements, with special emphasis on reducing the ambiguity search space. In addition, an algorithm which can effectively detect and correct the cycle slips is described as well. The algorithm utilizes additional position information provided by the INS, and applies a statistical technique known as the cumulative-sum (CUSUM) test that is very sensitive to abrupt changes of mean values. Results of simulation studies and field tests indicate that the algorithms are performed pretty well, so that the accuracy and performance of the integrated system can be maintained, even if cycle slips exist in the raw GPS measurements.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.800-807
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• 2010

Jack knifing accident of semi trailer vehicle is one of the most dangerous accident type because the vehicle cross over its lane by the accident. Jack knifing accident can be predicted and detected by GNSS precise relative positioning. But integer ambiguity resolution procedure is inevitable in GNSS precise relative positioning. In this paper, success rate improving method of integer ambiguity resolution is proposed for jack knifing accident prediction and detection of semi trailer vehicle, and proposed method is tested by simulation.

• Journal of KSNVE
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• v.7 no.5
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• pp.747-756
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• 1997

Wigner-Ville distribution which is a time-frequency analysis has a fatal drawback, when the signal has multiple components. This is the cross-talk and often causes a neagative value in the distribution. Wingner-Ville distriution is an expression of power, therefore the cross-talk must be avoided. Smoothing the Wigner-Ville distribution by convoluting it with a window, is most commonly used to reduce the cross-talk. There can be infinite number of distributions depending on the windows. But, the smoothing reduces resolution in time-frequency plane; this motives to design a more effective window in reducing cross-talk while remaining resolution. The domain in which the cross-talk and legitimate components can be easily distinguished, is the ambiguity function. In the ambiguity function domain, the legitimate components appear as linear lines passing through the orgine. But, the cross-talk is widely distributes in the ambiguity function plane. Based on the relative distributions of cross-talk and legitimate components, rotating window can be designed to minimize cross-talk. Applying the rotating window to the ambiguity function corresponds to smoothing the Wigner-Ville distribution. Therefore, the effects of rotating window is estimated in terms of the bias error due to smooting the Wigner-Ville distribution. By applying the rotating window, not only the Wigner-Ville distribution but also its properties are changed. The properties of the new distribution are checked, in order to complete analyzing the rotating window.

• Proceedings of the Korean Society for Language and Information Conference
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• 1995.02a
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• pp.121-126
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• 1995

A new method for Chinese word segmentation named Conditional F'||'&'||'BMM (Forward and Backward Maximal Matching) which incorporates both bigram statistics (ie., mutual infonllation and difference of t-test between Chinese characters) and linguistic rules for ambiguity resolution is proposed in this paper The key characteristics of this model are the use of: (i) statistics which can be automatically derived from any raw corpus, (ii) a rule base for disambiguation with consistency and controlled size to be built up in a systematic way.

• Proceedings of the KSPS conference
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• 2003.10a
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• pp.79-82
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• 2003

The purpose of this study is to examine the regions of the cerebrum that handles the lexical and idiomatic ambiguity. The stimuli sets consist of two parts, and each part has 20 sets of sentences. For each part, 10 sets are experimental conditions and the other 10 sets are control conditions. Each set has two sentences, the 'context' and 'target' sentences, and a sentence-verification question for guaranteeing patients' concentration to the task. The results based on 15 patients showed that significant activation is present in the right frontal lobe of the cerebral cortex for both kinds of ambiguity. It means that right hemisphere participates in the resolution of ambiguity, and there are no regions specified for lexical ambiguity or idiomatic ambiguity alone.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.12
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• pp.1036-1043
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• 2001

It is well-known that positioning accuracy can be improved by the use of carrier phase of GPS up to the centimeter level. In order to obtain good accuracy, we need to know integer ambiguity in the carrier phase accurately. In this paper, we propose a fast ambiguity determination method(FADM) which combines Kalman filtering and the search method, and show the improvement of the positioning performance by static and kinematic simulation compared with known methods such as Kalman filtering, LSAST (Least Squares Ambiguity Search Technique), ARCE(Ambiguity Resolution with Constratint Equation), LLL(Lenstra, Lenstra, and Lovasz) algorithms.

• Journal of KIISE:Software and Applications
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• v.26 no.9
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• pp.1132-1140
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• 1999

한국어에서 보조사로 인해 발생하는 격 모호성(case ambiguity) 문제를 해결하는 알고리즘을 개발하였다. 이 알고리즘은 용언의 하위범주화 사전, 용언과 그 용언의 보어가 되는 체언간의 선택 제약, 체언의 의미 정보를 제공하는 시소러스 등의 구문.의미 지식과 더불어 몇 가지의 휴리스틱 규칙을 이용하며, 필수 보어의 생략이 흔한 한국어의 특성에 잘 대응한다. 중규모의 하위범주화 사전 및 시소러스를 이용한 실험에서 만족할 만한 성능을 보였다.Abstract An algorithm is proposed for the resolution of case ambiguity caused by the use of auxiliary postpositions in Korean language. The algorithm utilizes verb dictionary which provides subcategorization information and selectional restrictions, and the thesaurus as well as a set of simple heuristic rules. The algorithm is appropriate for Korean language where required complements are often omitted. The algorithm performed successfully in an experiment using medium-sized subcategorization dictionary and thesaurus.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.253-262
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• 2021

Global Navigation Satellite Systems (GNSS) based precise positioning using Real Time Kinematic (RTK) technique has been proposed as an enabler of the formation operation of moving vehicles. In RTK methods, the integer ambiguity of GNSS carrier phase measurements must be resolved. Although there have been many proposed algorithms for the integer ambiguity resolution, the widelane combination of carrier phase measurements and LAMBDA methods have gained the most popularity in literatures when dual frequency GNSS measurements were used. In this paper, we evaluated five alternative methods to determine relative positions of moving base and rover receivers; the round-off scheme of widelane carrier phase, instant least-squares and Kalman filter-based LAMBDA with widelane carrier phase, instant least-squares and Kalman filter-based LAMBDA with dual frequency measurements. The paper presented the performance of each method using flight test data, which showed their strength and weakness in the aspects of time-to-first-fix, ambiguity resolution success ratio, and relative position errors. Based on that, we provided practical recommendations of RTK operations for moving vehicles.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.235-243
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• 2018

Conventional Real Time Kinematics (RTK) collect measurements in stationary state for several minutes to resolve the integer ambiguity in the carrier phase measurement or resolve the integer ambiguity on the move assuming low maneuvering movement. In this paper, an On The Move-RTK (OTM-RTK) technique that resolves the integer ambiguity on the move for fast and precise positioning of ground vehicles such as high maneuvering vehicles was proposed. The OTM-RTK estimates the precise amount of movement between epochs using the carrier phase measurements acquired on the move, and by using this, resolves the integer ambiguity within a short period of time by evaluating the integer ambiguity candidates for each epoch. This study analyzed the integer ambiguity resolution performance using field driving experiment data in order to verify the performance of the proposed method. The results of the experiment showed that the precise trajectory including the initial position bias can be obtained prior to resolving the integer ambiguity, and after resolving the integer ambiguity on the move, it was possible to obtain the bias-corrected precise position solution. It was confirmed that the integer ambiguity can be resolved by collecting measurements of about 10 epochs from the moving vehicle using a dual frequency receiver.